Added migration for temporary index on pages deployments

changelogs/unreleased/325285-tmp-index-to-file-store.yml

+---
+title: Add index on file_store for pages_deployments table
+merge_request: 58355
+author:
+type: performance

db/migrate/20210401134157_add_index_to_pages_deployments.rb

+# frozen_string_literal: true
+
+class AddIndexToPagesDeployments < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_pages_deployments_on_file_store_and_id'
+
+  def up
+    add_concurrent_index :pages_deployments, [:file_store, :id], name: INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index_by_name :pages_deployments, INDEX_NAME
+  end
+end

db/schema_migrations/20210401134157

+02f8ed673f87cb2528022d8352a1551b3c7250986d6dc387c1bbdfbc71123272
\ No newline at end of file

db/structure.sql

@@ -23457,6 +23457,8 @@ CREATE INDEX index_packages_tags_on_package_id_and_updated_at ON packages_tags U
 
 CREATE INDEX index_pages_deployments_on_ci_build_id ON pages_deployments USING btree (ci_build_id);
 
+CREATE INDEX index_pages_deployments_on_file_store_and_id ON pages_deployments USING btree (file_store, id);
+
 CREATE INDEX index_pages_deployments_on_project_id ON pages_deployments USING btree (project_id);
 
 CREATE INDEX index_pages_domain_acme_orders_on_challenge_token ON pages_domain_acme_orders USING btree (challenge_token);